Abstract
Background:
There is literature on epidemiologic trends in acute primary tendon ruptures. However, most of the data used in the literature is centered in Europe or Canada, whereas there has been little analysis of trends in primary tendon ruptures in the United States (US), especially data collected after 2010.
Purpose:
To report the epidemiology of upper and lower extremity acute primary tendon ruptures presenting to emergency departments (ED) in the US and compare incidence ratios based on race using the National Electronic Injury Surveillance System (NEISS) Database.
Study Design:
Descriptive epidemiology study.
Methods:
The NEISS database was queried for acute primary tendon ruptures in the US from 2001 to 2020. National estimates (N) and estimated incidence ratios (IR) reported as per 100,000 person-years at risk (PYR) for acute primary tendon ruptures were calculated using NEISS sample estimates (n) and US Census Bureau population estimates. Temporal trends in annual IRs throughout the study period were assessed with regression analyses.
Results:
From 2001 to 2020, there were an N of 235,189 (95% CI, 186,833-283,546) ED visits for acute tendon ruptures in the US, which occurred in a population of 6,183,899,410 person-years for an overall IR of 3.80 PYR (95% CI, 3.02-4.59). Acute primary Achilles (38.2%), biceps brachii (16.2%), and patellar tendon (12.7%) ruptures were the most common injuries. Black patients had the highest overall IR, with an N of 38,679 ruptures (95% CI, 21,552-55,807) occurring in this group for an overall IR of 4.78 PYR (95% CI, 2.66-6.89). The IR of lower extremity tendon ruptures was significantly higher in Black patients, but did not differ for upper extremity tendon ruptures. The annual incidence of all tendon ruptures in the US increased significantly from 2001 to 2020, with an average annual percent of 3 (95% CI, 2.3-3.7; P < .0001).
Conclusion:
Our study demonstrated that the IR of acute primary tendon ruptures presenting to the ED in the US has increased from 2001 to 2020. Black/African-American individuals have an increased IR compared with White populations.
Keywords: epidemiology, National Electronic Injury Surveillance System, rupture, sports, tendon
Tendons are the integrative forces between the muscular and osseous anatomy of the body, allowing transmission of muscular forces for movement of the skeleton. 14 Aging, overuse secondary to physical training, and corticosteroid use have been suggested to play a role in tendon degeneration and injury. 14 Furthermore, with the growing role of sports and physical activity in developed countries, the incidence of tendon injuries is inevitably rising. 4 Commonly known risk factors for tendon injury have previously been elucidated and include, but are not limited to, race, male sex, age, participation in recreational sports, obesity, and type 2 diabetes.14,15 Acute tendon ruptures affect quality of life, participation in competitive athletics, and increase health care costs. 3
The existing epidemiological literature concerning acute primary tendon ruptures is often limited to the Achilles and patellar tendons. Furthermore, to our knowledge, these studies are largely based in Europe or Canada and were conducted6,8,11,17,19,28 before 2010. Lemme et al 10 provided an update on the incidence of tendon ruptures in the United States (US) using the National Electronic Injury Surveillance System (NEISS) database, but focused on Achilles tendon injuries. Similarly, Fredericks et al 5 described descriptive data of patellar tendon ruptures alone based specifically on a military database. Owens et al 20 showed that race is associated with increased susceptibility to tendon injuries and that Black patients are at a higher risk compared with a reference group of White patients and “Other” races. Although providing great insight into a possible important epidemiologic difference, this study was based on the Defense Medical Epidemiology Database. The military population is a highly active group of individuals who are likely to put increased stressors on the body and specifically tendons due to rigorous training. Therefore, this study may not be generalizable to the US population.
This study aimed to identify the incidence of acute primary tendon ruptures presenting to emergency departments (EDs) in the US, using the NEISS database. Secondarily, this study aimed to describe whether racial differences exist in the incidence of tendon ruptures. We hypothesized that there would be no significant difference in the incidence of tendon ruptures between races.
Methods
This descriptive epidemiological study was conducted by the orthopaedic surgery physicians who together co-authored this paper, a retrospective analysis of the NEISS, a public database operated by the US Consumer Product Safety Commission (CPSC). This system is used to gather product-related injury data from a probability sample of approximately 100 hospital EDs throughout the US and its territories. This sample of hospitals includes a geographically diverse community and academic institutions, which have been selected by the CPSC to provide an important representation of all other hospitals of its size and unique characteristics in the US. Thus, they provide a nationally representative sample of US hospital EDs from which nationwide injury estimates can be made.26,29 Each participating facility gathers and reports information for every ED visit associated with a consumer product and/or recreational activity, including information about the patient, the incident, the injury, and any products or activities associated with the injury. Each case is assigned a statistical weight based on the inverse probability of being selected. This allows for the conversion of cases reported in the dataset (unweighted records, n) to national injury estimates (weighted estimates, N), by accounting for the NEISS stratified probability sampling design. The NEISS database has been widely used to analyze various types of injuries and is an established model for epidemiological surveillance of musculoskelet al injuries.10,12,13,29
The NEISS database contains patient characteristics, including age, sex, and race. Race categories in the NEISS database are as follows: (1) White; (2) Black/African American; (3) Other; (4) Asian; (5) American Indian/Alaska Native (AI/AN); and (6) Native Hawaiian/Pacific Islander (NH/PI). The “Other” race is coded when either the ED records indicate >1 race (eg, multiracial, biracial) or if the race stated in the ED record is not any of the aforementioned categories. There is also an ethnicity variable, which is separately coded, apart from race, as Hispanic or non-Hispanic. This unique variable was added in 2018, and thus, a majority of cases do not include this information. There was a very small number of cases involving AI/AN and NH/PI individuals, insufficient to permit reliable analyses of these racial groups individually. Therefore, the race categories were regrouped as follows: AI/AN individuals were added to the category “Other,” and NH/PI individuals were added to the category “Asian.” Thus, the race categories for final analysis included (1) White, (2) Black/African American, (3) Other (including “Other” and “AI/AN”), and (4) Asian/PI (“Asian,” including “Asian” and “NH/PI”). Furthermore, the NEISS database allows for the categorization of tendon rupture locations. Thus, the incidence of tendon ruptures was further categorized by anatomic location.
In short, all cases of ED visits in the US from 2001 to 2020 were considered for selection, and a combination of computer-assisted and manual review of case narratives was used to select only those cases with a clear diagnosis of an acute primary tendon rupture. Cases without a clear diagnosis (including any “rule out,”“possible,” or “suspected” diagnosis) and cases with an alternate diagnosis were excluded. Alternate diagnoses that were excluded were those describing muscle (rather than tendon) injuries, tendon strains/sprains, tendinitis, and recurrent/chronic injuries.
Statistical Analysis
Statistical analysis was performed using the survey data commands (svyset) in Stata/IC Version 17.0 (StataCorp), accounting for sample weights and the complex survey design. Results are reported as numbers of unweighted cases (n) and/or as weighted national estimates (N) with corresponding 95% CIs. National estimates (N) are calculated using NEISS sample weights and are utilized in all statistical analyses. Estimated incidence rates (IRs) are expressed as the number of injuries per 100,000 person-years at-risk (PYR) and are calculated as the number of estimated injuries (N) divided by PYR. US Census Bureau population estimates were used to calculate PYR during the study period. 30 Incidence rate ratios (IRRs) are reported and represent unitless expressions of risk used for the comparison of IRs between 2 distinct subgroups, with the IR of an identified referent subgroup serving as the denominator. IRRs among race, sex, and age groups are reported. Patients were split into 4 different age groups for comparisons: (1) children, 0-17 years; (2) young adults, 18-34 years; (3) middle-aged adults, 35-54 years; and (4) older adults, 55+ years. Chi-square tests were used to compare estimated IRs between groups. Student t test/analysis of variance and design-adjusted Rao-Scott chi-square analysis were used for direct comparisons of means for continuous variables and proportions for categorical variables, respectively.24,25 Temporal trends in annual IRs throughout the study period were assessed with regression analyses (Joinpoint Regression Program, Version 4.9.1.0; National Cancer Institute). 7 The average annual percent change (AAPC) estimates are presented to indicate the magnitude and direction of trends in injury rates for each period as determined by Joinpoint regressions. P < .05 was the threshold for statistical significance.
Results
After exclusions, a total of 5765 unweighted cases of upper (n = 1652) and lower (n = 4113) extremity tendon ruptures were identified, corresponding to an N of 235,189 tendon ruptures (95% CI, 186,833-283,546). From 2001 to 2020, there were an estimated 235,189 (95% CI, 186,833-283,546) ED visits for acute primary tendon ruptures in the US, which occurred in an at-risk population of 6,183,899,410 person-years for an overall IR of 3.80 PYR (95% CI, 3.02-4.59). A rupture of the Achilles tendon was the most common injury, accounting for 38.2% of all cases, followed by ruptures of the biceps tendon (16.2%) and the patellar tendon (12.7%). Men accounted for the majority of cases (82%), and the overall injury rate in men was 4.7 times that of women (IRR, 4.7 [95% CI, 3.08-7.17]; P < .05). The overall mean age was 43.7 years. Injury estimates, overall and sex-specific IRs, and mean age for the different types of tendon ruptures are outlined in Table 1.
Table 1.
Estimates, Overall and Sex-Specific Incidence Rates, and Mean Age of the Different Types of Tendon Ruptures Presenting to United States EDs From 2001 to 2020 a
| Tendon Rupture | National Estimate, N | Unweighted cases, n | % | Overall IR, N/105 | Male IR, N/105 | Female IR, N/105 | M: F IRR | M: F IRR, 95% CI | Mean Age, Years | Mean Age, Years, 95% CI |
|---|---|---|---|---|---|---|---|---|---|---|
| Achilles tendon rupture | 89,917 | 2,425 | 38.2 | 1.45 | 2.46 | 0.48 | 5.1 | 2.9-9.3 b | 38.7 | 38-39.3 |
| Biceps tendon rupture | 38,182 | 800 | 16.2 | 0.62 | 1.12 | 0.13 | 8.5 | 4.8-15.3 b | 51.2 | 49.6-52.9 |
| Patellar tendon rupture | 29,746 | 777 | 12.7 | 0.48 | 0.85 | 0.12 | 7.1 | 4.1-12.2 b | 39.9 | 38.1-41.7 |
| Rotator cuff tendon tear | 21,824 | 422 | 9.3 | 0.35 | 0.49 | 0.22 | 2.2 | 1.4-3.4 b | 48.5 | 46.2-50.7 |
| Quadriceps tendon rupture | 19,234 | 495 | 8.2 | 0.31 | 0.56 | 0.07 | 8.2 | 4-16.7 b | 56 | 53.8-58.1 |
| Forearm/wrist/hand tendon rupture | 14,286 | 340 | 6.1 | 0.23 | 0.34 | 0.13 | 2.6 | 1.7-4 b | 38 | 35.7-40.3 |
| Hamstring tendon rupture | 7325 | 163 | 3.1 | 0.12 | 0.17 | 0.06 | 2.7 | 1.5-5.1 b | 46.1 | 42.4-49.8 |
| Proximal calf tendon rupture | 2897 | 73 | 1.2 | 0.05 | 0.06 | 0.04 | 1.6 | 0.7-4 | 40.4 | 37.6-43.2 |
| Foot/ankle tendon rupture | 1605 | 30 | 0.7 | 0.03 | 0.04 | 0.01 | 3.3 | 1-10.7 b | 43 | 38.8-47.2 |
| Triceps tendon rupture | 1195 | 31 | 0.5 | 0.02 | 0.04 | <0.01 | 12 | 3.3-43.1 b | 44.4 | 37.4-51.4 |
| Hip/proximal thigh tendon rupture | 1049 | 20 | 0.5 | 0.02 | <0.01 | 0.03 | 0.1 | 0-1.5 | 62.7 | 53-72.5 |
| Pectoralis tendon rupture | 820 | 25 | 0.4 | 0.01 | 0.03 | <0.01 | 25.3 | 3.3-191 b | 36.1 | 27-45.3 |
| Unspecified tendon rupture | 7109 | 164 | 3 | |||||||
| Total/overall | 235,189 | 3653 | 100 | 3.80 | 6.34 | 1.35 | 4.7 | 3.1-7.2 b | 43.7 | 42.6-44.9 |
Proximal calf tendon rupture includes the proximal gastrocnemius and plantaris tendons. Foot/ankle tendon rupture includes the foot/ankle extensor and peroneal tendons. Hip/proximal thigh tendon rupture includes the hip abductor and hip flexor tendons. Unspecified tendon ruptures include those cases in which the tendon involved was not specified in the NEISS case narrative, but the general location was indicated by the body part code. All IRs are expressed per 100,000 person-years. ED, emergency department; F, female; IR, incidence rate. IRR, incidence rate ratio; M, male; NEISS, National Electronic Injury Surveillance System; %, percentage of all tendon ruptures.
Indicates a statistically significant difference for men: women incidence rate ratios, with 95% CIs not including 1.
The race was specified in 71.4% of cases. Race data were unavailable for the remaining 28.6% of cases. Unweighted case numbers (n) and national estimates (N) for each racial category, before regrouping, are displayed in Table 2.
Table 2.
Number of Unweighted Records and Corresponding Weighted National Estimates of All Cases of Tendon Ruptures Presenting to United States EDs From 2001 to 2020, by Race Category (Before Regrouping) a
| Race | n | N [95% CI] | % |
|---|---|---|---|
| White | 2310 | 115,905 | 49.3 |
| [83,405 to 148,404] | |||
| Black/African American | 916 | 38,679 | 16.5 |
| [21,547 to 55,812] | |||
| Other b | 231 | 8716 | 3.7 |
| [5608 to 11,824] | |||
| Asian | 112 | 4061 | 1.7 |
| [698 to 7424] | |||
| AI/AN | 12 | 470 | 0.2 |
| [–122 to 1062] | |||
| NH/PI | 2 | 90 | <0.1 |
| [–60 to 240] | |||
| Unknown/Unspecified | 2182 | 67,269 | 28.6 |
| [41,863 to 92,675] | |||
| Total | 5765 | 235,189 | 100 |
| [186,833 to 283,546] |
% represents the column percentage for all cases of tendon ruptures identified over the study period.
AI/IN, American Indian/Alaska Native; ED, emergency department; n, unweighted cases; N, weighted national estimate; NH/PI, Native Hawaiian/Pacific Islander.
Other is coded when either the ED record indicates >1 race (eg, multiracial, biracial) or when the race stated in the ED record is not White, Black, Asian, AI/AN, or NH/PI.
Because of the small number of cases involving AI/AN and NH/PI individuals, these race categories were regrouped for further analysis, as described in the Methods. Hispanic ethnicity status was specified in just 12.7% of cases. These data were unavailable for the remaining 87.3% of cases.
The largest total number of injuries occurred in White patients, with an N of 115,905 tendon ruptures (95% CI, 83,461-148,348) in this group for an overall IR of 2.40 PYR (95% CI, 1.73-3.07). Black patients had the highest overall IR, with an N of 38,679 ruptures (95% CI, 21,552-55,807) occurring in this group for an overall IR of 4.78 PYR (95% CI, 2.66-6.89). An N of 9186 ruptures (95% CI, 5881-12,491) occurred in patients of the “Other” race for an overall IR of 4.35 PYR (95% CI, 2.78-5.91). Finally, N of 4151 ruptures (95% CI, 777-7,524) occurred in Asian patients for an overall IR of 1.29 PYR (95% CI, 0.24-2.32). When compared with White patients, the overall injury rate was significantly higher among Black patients (IRR, 1.99 [95% CI, 1.06-3.76]; P < .05) and Other patients (IRR, 1.81 [95% CI, 1.09-3.03]; P < .05) and was similar in Asian patients (IRR, 0.53 [95% CI, 0.27-1.06]; P > .05). There were no statistically significant differences in overall incidence among Black and Other patients, with the “Other” race as the referent (IRR, 1.10 [95% CI, 0.62-1.95]; P > .05). Additional race-specific demographic and incident information for all tendon ruptures reported over the study period is shown in Table 3.
Table 3.
Tendon Rupture Estimates, Incidence Rates, and Patient and Incident Characteristics for All Tendon Ruptures Presenting to United States EDs, 2001-2020, by Race a
| All Tendon Ruptures | White | Black | Other | Asian/PI | P | |
|---|---|---|---|---|---|---|
| n | 5765 | 2310 | 916 | 243 | 114 | |
| N | 235,189 | 115,905 | 38,679 | 9186 | 4151 | |
| [95% CI] | [186,833-283,546] | [83,461-148,348] | [21,552-55,807] | [5881-12,491] | [777-7,524] | |
| Incidence rate, per 100,000 | 3.80 | 2.40 | 4.78 | 4.35 | 1.28 | |
| [95% CI] | [3.02-4.59] | [1.73-3.07] | [2.66-6.89] | [2.78-5.91] | [0.24-2.32] | |
| Sex, % | .0013 | |||||
| Male | 82 | 79.9 | 85.6 | 81 | 79.7 | |
| Female | 18 | 20.1 | 14.4 | 19 | 20.3 | |
| Age distribution, years, % | <.0001 | |||||
| 0-17 | 3.4 | 3.5 | 3.2 | 5.8 | 2.3 | |
| 18-34 | 28.2 | 23.5 | 37.3 | 35.2 | 49.7 | |
| 35-54 | 44.4 | 42.7 | 48.2 | 47.4 | 44.4 | |
| 55+ plus | 24 | 30.3 | 11.3 | 11.6 | 3.6 | |
| Anatomic location of tendon rupture, % | <.0001 | |||||
| Upper extremity | 33.2 | 41.3 | 16.7 | 32.8 | 12.6 | |
| Lower extremity | 66.8 | 58.7 | 83.3 | 67.2 | 87.4 |
Percent totals may not sum to 100% because of rounding. P values indicate the differences between White, Black, Other, and Asian races for each of the listed variables. EDs, emergency departments; n, unweighted cases; N, national estimates; PI, Pacific Islander.
Lower Extremity Tendon Ruptures
Race-specific national estimates and IRs for the lower extremity tendon ruptures are shown in Table 4. Black and Other patients had a significantly higher rate of all lower extremity tendon ruptures when compared with White patients. When looking at specific types of lower extremity tendon ruptures, injury rates were significantly higher among Black and Other patients (when compared with White patients) for Achilles and patellar tendon ruptures (Table 4).
Table 4.
Estimates and Incidence Rates of All Upper and Lower Extremity Tendon Ruptures Presenting to the United States EDs From 2001-2020 a
| n | N | PYR | IR (95% CI) | IRR (95% CI) | ||
|---|---|---|---|---|---|---|
| Achilles | ||||||
| Black | 445 | 18,985 | 809409035 | 2.35 (1.30 to 3.40) | 3.06 b (1.43 to 6.54) | |
| Other | 99 | 3483 | 211353282 | 1.65 (0.94 to 2.36) | 2.15 b (1.12 to 4.12) | |
| Asian | 85 | 2931 | 324855681 | 0.90 (0.08 to 1.73) | 1.18 (0.42 to 3.30) | |
| White | 805 | 37,079 | 4838281412 | 0.77 (0.49 to 1.04) | Reference | |
| Patellar | ||||||
| Black | 223 | 8712 | 809409035 | 1.08 (0.52 to 1.63) | 4.74 b (1.73 to 12.96) | |
| Other | 38 | 1318 | 211353282 | 0.62 (0.33 to 0.92) | 2.74 b (1.28 to 5.88) | |
| Asian | 7 | 340 | 324855681 | 0.10 (–0.01 to 0.21) | 0.46 (0.21 to 1.03) | |
| White | 225 | 10,994 | 4838281412 | 0.23 (0.16 to 0.29) | Reference | |
| Quadriceps | ||||||
| Black | 56 | 2759 | 809409035 | 0.34 (0.14 to 0.54) | 1.58 (0.73 to 3.42) | |
| Other | 15 | 490 | 211353282 | 0.23 (0.05 to 0.41) | 1.07 (0.45 to 2.56) | |
| Asian | 2 | 32 | 324855681 | 0.01 (–0.01 to 0.03) | – | |
| White | 207 | 10,458 | 4838281412 | 0.22 (0.13 to 0.30) | Reference | |
| Hamstring | ||||||
| Black | 15 | 426 | 809409035 | 0.05 (0.01 to 0.09) | 0.59 (0.27 to 1.29) | |
| Other | 8 | 326 | 211353282 | 0.15 (0 to 0.31) | 1.73 (0.47 to 6.41) | |
| Asian | 4 | 212 | 324855681 | 0.07 (–0.01 to 0.14) | 0.73 (0.26 to 2.07) | |
| White | 84 | 4315 | 4838281412 | 0.09 (0.05 to 0.13) | Reference | |
| Proximal calf | ||||||
| Black | 5 | 113 | 809409035 | 0.01 (0 to 0.03) | 0.51 (0.15 to 1.74) | |
| Other | 5 | 230 | 211353282 | 0.11 (–0.01 to 0.23) | 3.95 (0.55 to 28.22) | |
| Asian | 1 | 32 | 324855681 | 0.01 (–0.01 to 0.03) | – | |
| White | 30 | 1334 | 4838281412 | 0.03 (0.01 to 0.05) | Reference | |
| Foot/ankle | ||||||
| Black | 4 | 198 | 809409035 | 0.02 (0 to 0.05) | 1.92 (0.38 to 9.58) | |
| Other | 1 | 69 | 211353282 | 0.03 (–0.03 to 0.10) | – | |
| Asian | 0 | 0 | 324855681 | – | – | |
| White | 10 | 615 | 4838281412 | 0.01 (0 to 0.02) | Reference | |
| Hip/proximal thigh | ||||||
| Black | 0 | 0 | 809409035 | – | – | |
| Other | 1 | 55 | 211353282 | 0.03 (–0.03 to 0.08) | – | |
| Asian | 0 | 0 | 324855681 | – | – | |
| White | 14 | 848 | 4838281412 | 0.02 (0 to 0.04) | Reference | |
| Total lower extremity c | ||||||
| Black | 768 | 32,309 | 809409035 | 3.98 (2.19 to 5.77) | 2.83 b (1.36 to 5.91) | |
| Other | 170 | 6171 | 211353282 | 2.92 (1.84 to 4) | 2.08 b (1.19 to 3.62) | |
| Asian | 100 | 3628 | 324855681 | 1.12 (0.15 to 2.08) | 0.79 (0.34 to 1.83) | |
| White | 1425 | 68,006 | 4838281412 | 1.41 (0.96 to 1.85) | Reference | |
IR is expressed per 100,000 PYR. The IRR is expressed with the White race as the referent.
The hyphen indicates an inadequate sample population. EDs, emergency departments; IR, incidence rate; IRR, incidence rate ratio; n, unweighted cases; N, weighted national estimate; PYR, person-years at-risk.
Indicates a statistically significant difference in IR when compared with the White race.
Because the cases with “unspecified” upper extremity tendon ruptures are not shown, total values may exceed the sum of the individual tendon values for each race.
Upper Extremity Tendon Ruptures
Race-specific national estimates and IRs for the upper extremity tendon ruptures are shown in Table 4. The overall incidence rate of all upper extremity tendon ruptures among Black and Other patients was similar to that among White patients and was significantly lower among Asian patients when compared with White patients (Table 4). When looking at specific types of upper extremity tendon ruptures, injury rates among Black and Asian patients were significantly lower than those of White patients for biceps tendon ruptures and were significantly higher among Other patients (when compared with White patients) for forearm/wrist/hand tendon ruptures. No other statistically significant differences were observed among racial groups for the different types of upper extremity tendon ruptures.
Trends
The annual incidence of all tendon ruptures in the US increased significantly from 2001 to 2020 (AAPC, 3 [95% CI, 2.3 to 3.7]; P < .0001). Stratified by race, the annual incidence increased significantly among White (AAPC, 2 [95% CI, 1 to 3.1]; P = .0008) and Black (AAPC, 3.3 [95% CI, 1.5 to 5.2]; P = .0012) patients, and there was no significant difference in the rate of annual increase between these race groups (P = .203). The annual incidence was unchanged in Other (AAPC, 0.6 [95% CI, –2.6 to 4]; P = .6893) and Asian (AAPC, –2.5 [95% CI, –5.9 to 1]; P = .1457) patients over the study period. Race-specific trends in the annual incidence of tendon ruptures are displayed in Table 3.
Discussion
The major findings of our study demonstrated that Achilles tendon ruptures have been the most common acute tendon ruptures that present to the ED overall, and men have accounted for the majority of ED visits compared with women for acute ruptures. Although the White population accounted for the majority of acute tendon ruptures presenting to the ED, the black population had a higher incidence rate of acute tendon ruptures. The Black and other minority races had a significantly higher injury rate of lower extremity tendon ruptures when compared with White individuals, with Achilles and patellar tendon tears further demonstrating a significant difference compared with other lower extremity tendons. The difference in rates of presenting ruptures was not as apparent in the upper extremities, although biceps tendon ruptures were significantly lower among black and Asian patients when compared with white patients.
Acute primary tendon ruptures are debilitating injuries with an associated burden of cost, effect on quality of life, and significant implications for competitive athletes.18,22 These injuries often result secondary to sudden contractile forces, which overcome the ultimate strength of the specific tendon. Age-related degeneration, prolonged corticosteroid use, insufficient periods of recovery between exercise regimens, as well as excessive loads during exercise, have been labeled as risk factors predisposing individuals to tendon ruptures.1,14,15 There is scarce literature concerning the epidemiology of all primary tendon ruptures presenting to EDs in the US, as well as limited comparisons with regard to injury risk based on age, sex, and race. In the present study, the overall IR of acute primary tendon ruptures presenting to EDs in the US was 3.80 PYR (95% CI, 3.02-4.59). Moreover, Black/African-American individuals and “Other” races had a significantly higher IR of acute primary tendon ruptures, compared with White individuals.
The present study describes the incidence of various types of tendon ruptures in the US between 2001 and 2020 (Table 1). The overall IR of acute primary tendon ruptures presenting to EDs in the US was 3.80 PYR (95% CI, 3.02-4.59). Furthermore, the estimated incidence of Achilles and patellar tendon injuries was the first and third most common of all tendon ruptures. The reported incidence of Achilles tendon rupture based on studies out of Europe ranges from 6 to 37 per 100,000 person-years.6,15 Lemme et al 10 identified an overall Achilles tendon rupture incidence of 2.1 per 100,000 person-years between 2012 and 2016 in the US. This is similar compared with our study in which the incidence of Achilles tendon rupture was 1.45 per 100,000 person-years between 2001 and 2020. Similar to our findings, Pope et al 23 reported an incidence rate of patellar tendon rupture of 0.68 per 100,000 person-years. However, previous literature also demonstrates a higher estimated incidence of patellar tendon ruptures.5,20 This is presumably because these studies are based on a military population, who inherently have increased physical demands compared with the general population. Reduced intervals of rest and increased physical training have been shown to increase the risk of acute tendon ruptures.14,23 Although still clinically relevant, the less common tendon ruptures—that is, proximal gastrocnemius, triceps, et cetera—likely have heterogeneity between studies because of the rarity of these injuries. These comparisons support the validity and accuracy of our results using the NEISS database and provide an important updated epidemiological estimate of these injuries in the general population.
Previous studies have examined the differences in tendon rupture between sexes. Men appear to have a higher risk of tendon ruptures than women. 21 Our study supports this trend. Table 1 demonstrates a consistently statistically significant difference that favors men in the incidence of tendon ruptures in both upper and lower extremities, with the only exceptions demonstrated in categories of proximal calf and hip/proximal thigh. Despite recent positive changes in gender equality with regard to sports participation, women continue to be underrepresented in sports participation. 4 As demonstrated by Eime et al, 4 sports registration between 2015 and 2019 revealed a slow but progressive decrease in the gap between male and female participation in public recreational sports. However, despite the improvements seen over this period, by 2019 the participation rate for men (17.1%) remained nearly double that for women (9.8%). The relatively higher ratio of men in sports activities may explain the higher incidence of tendon ruptures compared with women, although further analysis comparing genders in sports is required to better evaluate this correlation.
Scarce data exist on the racial differences in the incidence of tendon ruptures. Table 2 summarizes the national incidence of all tendon ruptures stratified by race, with the highest gross number among those who identified as White. However, this does not take into account the relative total populations of each race. Table 3 proves the incidence rate of each race while considering specific populations at risk and shows that Black individuals have the highest incidence rate of acute tendon ruptures. These results are in agreement with the report by Owens et al, 20 which identified a higher incidence of major tendon rupture among Black soldiers over a 4-year time frame. The cause of higher incidence rates of tendon ruptures seen in Black individuals is likely multifaceted and beyond the scope of the present study. Tendon injuries are often due to acute, sudden contractile forces that overcome the ultimate strength of the specific tendon. However, overuse, age-related degeneration, genetics, and corticosteroids have all been described as risk factors for tendon injury.5,14,15 Furthermore, previous literature has shown that there are discrepancies with regard to access to primary care physicians between racial groups.9,16,27 Black and “Other” patients may have a higher IR of acute primary tendon ruptures presenting to EDs in the present study, secondary to social factors—including poor access to primary care physicians in an outpatient setting. However, there are biological risk factors as well, including but not limited to genetics, diabetes, nutritional status, and renal disease.
Aging is also an influencing factor in predisposition to acute tendon injuries. In agreement with previous literature and our study, Owens et al 20 showed that men have a higher incidence of tendon rupture, especially in the 30 to 40-year-old age group.This is likely explained by the fact that tendons begin to undergo degenerative changes as early as the third decade of life. 14 In combination with overuse, this sets the ideal environment for tendon rupture in the above-mentioned age groups. This also stands for our study, in which individuals aged 35 to 54 years had a higher incidence rate of tendon ruptures. Sports-related injury was reported as the most common location of injury. Hence, it can be concluded that individuals in this age group who partake in regular physical activity have a higher predilection for tendon injury.
Our data found no clear difference in rupture risk in terms of upper versus lower extremity tendons. Although the most common ruptures encountered are those of Achilles and patellar tendons, biceps brachii and rotator cuff tendon ruptures are encountered more often than most other lower extremity ruptures (Table 1). The reason for these higher frequencies may be due to their larger roles in recreational activities. To elaborate, the Achilles and patellar tendons are pivotal for mobilization in nearly all sporting activities, while the biceps and rotator cuff tendons are heavily relied upon in racquet sports. These higher stresses would reasonably lead to increased incidence rates of ruptures.
Our study is not without limitations. The strength of our study is that it is a population-based study and is not defined by a specific cohort of individuals. Furthermore, the similarity of the incidence rates of tendon ruptures in our study compared with previous literature increases its validity. Furthermore, the NEISS database is composed entirely of ED encounters and does not include tendinous injuries, which were evaluated and treated in alternate care settings such as outpatient and/or urgent care clinics. Moreover, certain tendon ruptures are inherently less likely to present to the ED than others. For example, a rotator cuff tendon tear or biceps tendon tear is less likely to affect function compared with a quadriceps tendon or patellar tendon tear. Thus, the former patient would be more likely to seek care in the outpatient setting instead. Moreover, some diagnoses may have been missed at the initial ED visits if the providers believed that the injury was a strain that could be treated conservatively. Again, these patients would likely seek care at a later date in the outpatient setting. Therefore, the estimated incidence rates in this study likely represent conservative estimates. The accuracy of the data reported in this study is also reliant upon accurate coding and correctness of the case narrative descriptions, inherently prone to reporter bias. The overall low incidence of certain types of tendon ruptures (eg, foot and ankle tendon ruptures, etc) makes it difficult to compare these outcomes based on racial identification. However, the NEISS database is an established model for epidemiological surveillance of musculoskelet al injuries, and its strengths include its large scale, heterogeneous patient population, and substantial external validity. 2 The explanation of causality in racial differences in acute primary tendon ruptures is beyond the scope of our study. This would require specific information about sports participation, duration/cycles per week, genetic differences between populations, et cetera. In addition, our study did not consider risk factors that would not be reported upon presentation to the ED. For instance, there is no way to evaluate the differences in baseline activity levels for the patients presenting with acute tendon ruptures, and there is no record of preceding inflammatory states, such as tendinitis, before presentation. Finally, while this analysis represents the largest contemporary epidemiological study of tendon ruptures in the US (to the authors’ knowledge), the findings reported here may not translate to patients from other nations due to the unique sociodemographic context of the US population. Future studies analyzing the epidemiology of tendon ruptures will further assist us in achieving a better understanding of these diagnoses, which in turn may help develop preventative care.
Conclusion
Our study demonstrates that the incidence rate of acute primary tendon ruptures presenting to EDs in the US has increased from 2001 to 2020. Men and Black/African-American individuals have an increased incidence rate compared with women and White populations, respectively.
Footnotes
Final revision submitted April 15, 2025; accepted May 14, 2025.
The authors have declared that there are no conflicts of interest in the authorship and publication of this contribution. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.
Ethical approval was not sought for the present study.
References
- 1. Ackermann PW, Renström P. Tendinopathy in sport. Sports Health. 2012;4(3):193-201. doi: 10.1177/1941738112440957. PMID: 23016086 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2. Boden BP, Isaacs DJ, Ahmed AE, Anderson SA. Epidemiology of exertional rhabdomyolysis in the United States: analysis of NEISS database 2000 to 2019. Phys Sportsmed. 2022;50(6):486-493. doi: 10.1080/00913847.2021.1956288 [DOI] [PubMed] [Google Scholar]
- 3. Clark ST, Zhu M, Gamble GD, et al. Epidemiology of tendon and ligament injuries in Aotearoa/New Zealand between 2010 and 2016. Inj Epidemiol. 2020;7:5. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4. Eime R, Charity M, Harvey J, Westerbeek H. Five-year changes in community-level sport participation, and the role of gender strategies. Front Sports Act Living. 2021; 3:710666. doi: 10.3389/fspor.2021.710666. Erratum in: Front Sports Act Living. 2021; 3:798271. PMID: 34712951 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5. Fredericks DR, Slaven SE, McCarthy CF, et al. Incidence and risk factors of acute patellar tendon rupture, repair failure, and return to activity in the active-duty military population. Am J Sports Med. 2021;49(11):2916-2923. doi: 10.1177/03635465211026963. PMID: 34313493 [DOI] [PubMed] [Google Scholar]
- 6. Houshian S, Tscherning T, Riegels-Nielsen P. The epidemiology of Achilles tendon rupture in a Danish county. Injury. 1998;29(9):651-654. doi: 10.1016/s0020-1383(98)00147-8. PMID: 10211195 [DOI] [PubMed] [Google Scholar]
- 7. Kim HJ, Fay MP, Feuer EJ, et al. Permutation tests for joinpoint regression with applications to cancer rates. Stat Med. 2000;19:335-351. PMID: 10649300 [DOI] [PubMed] [Google Scholar]
- 8. Kraeutler MJ, Purcell JM, Hunt KJ. Chronic Achilles tendon ruptures. Foot Ankle Int. 2017; 38(8):921-929. doi: 10.1177/1071100717709570 [DOI] [PubMed] [Google Scholar]
- 9. Lee DC, Shi L, Wang J, Sun G. Usual source of care and access to care in the US: 2005 vs. 2015. PLoS One. 2023;18(1):e0278015. doi: 10.1371/journal.pone.0278015 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10. Lemme NJ, Li NY, DeFroda SF, et al. Epidemiology of Achilles tendon ruptures in the United States: athletic and nonathletic injuries from 2012 to 2016. Orthop J Sport Med. 2018;6(11):2325967118808238. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11. Levi N. The incidence of Achilles tendon rupture in Copenhagen. Injury. 1997; 28(4):311-313. doi: 10.1016/s0020-1383(96)00200-8. PMID: 9282189 [DOI] [PubMed] [Google Scholar]
- 12. Lyons JG, Mian HM, Via GG, Brueggeman DA, Krishnamurthy AB. Trends and epidemiology of knee extensor mechanism injuries presenting to United States emergency departments from 2001 to 2020. Phys Sportsmed. 2022;51(2):183-192. doi: 10.1080/00913847.2021.2024775. PMID: 34965844 [DOI] [PubMed] [Google Scholar]
- 13. Lyons JG, Mian HM. Epidemiology of atlas fractures in the United States: a 20-year analysis. J Craniovertebral Junction Spine. 2022;13:85-93. doi: 10.4103/jcvjs.jcvjs_164_21. PMID: 35386248 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14. Maffulli N, Renstrom P, Leadbetter W. Tendon injuries: basic science and clinical medicine. Springer; 2009:3-85. [Google Scholar]
- 15. Maffulli N, Waterston SW, Squair J, Reaper J, Douglas AS. Changing incidence of Achilles tendon rupture in Scotland: a 15-year study. Clin J Sport Med. 1999; 9(3):157-160. doi: 10.1097/00042752-199907000-00007. PMID: 10512344 [DOI] [PubMed] [Google Scholar]
- 16. Manuel JI. Racial/ethnic and gender disparities in health care use and access. Health Serv Res. 2018;53(3):1407-1429. doi: 10.1111/1475-6773.12705 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17. Matava MJ. Patellar tendon ruptures. J Am Acad Orthop Surg. 1996;4(6):287-296. doi: 10.5435/00124635-199611000-00001. PMID: 10797196 [DOI] [PubMed] [Google Scholar]
- 18. Murdock CJ, Ochuba AJ, Xu AL, et al. Operative vs nonoperative management of Achilles tendon rupture: a cost analysis. Foot Ankle Orthop. 2023;8(1):24730114231156410. doi: 10.1177/24730114231156410 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19. Nyyssönen T, Lüthje P, Kröger H. The increasing incidence and difference in sex distribution of Achilles tendon rupture in Finland in 1987–1999. Scand J Surg. 2008;97(3):272-275. doi: 10.1177/145749690809700312. PMID: 18812279 [DOI] [PubMed] [Google Scholar]
- 20. Owens B, Mountcastle S, White D. Racial differences in tendon rupture incidence. Int J Sports Med. 2007; 28(7):617-620. doi: 10.1055/s-2007-964837. PMID: 17357966 [DOI] [PubMed] [Google Scholar]
- 21. Paavola M, Kannus P, Järvinen M. (2005). Epidemiology of tendon problems in sport. In: Maffulli N, Renström P, Leadbetter WB, eds. Tendon Injuries. Springer; 2005:32-39. doi: 10.1007/1-84628-050-8_5 [DOI] [Google Scholar]
- 22. Parikh N, Martinez DJ, Winer I, Costa L, Dua D, Trueman P. Direct and indirect economic burden associated with rotator cuff tears and repairs in the US. Curr Med Res Opin. 2021;37(7):1199-1211. doi: 10.1080/03007995.2021.1918074 [DOI] [PubMed] [Google Scholar]
- 23. Pope JD, El Bitar Y, Plexousakis MP. Quadriceps tendon rupture. 2022. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2022. PMID: 29494011. [PubMed] [Google Scholar]
- 24. Rao JNK, Scott AJ. On chi-squared tests for multiway contingency tables with cell proportions estimated from survey data. Ann Stat. 1984;12:46-60. [Google Scholar]
- 25. Rao JNK, Thomas DR. The analysis of cross-classified categorical data from complex sample surveys. Sociol Methodol. 1988;18:213. [Google Scholar]
- 26. Schroeder T, Ault K. The NEISS sample (design and implementation) from 1997 to Present. Washington, DC US Consum Prod Saf Comm. 2001. Accessed May 1, 2022. https://www.cpsc.gov/s3fs-public/2001d010-6b6.pdf
- 27. Sharma R, Tinkler S, Mitra A, Pal S, Susu-Mago R, Stano M. State Medicaid fees and access to primary care physicians. Health Econ. 2018;27(3):629-636. doi: 10.1002/hec.3591 [DOI] [PubMed] [Google Scholar]
- 28. Suchak AA, Bostick G, Reid D, Blitz S, Jomha N. The incidence of Achilles tendon ruptures in Edmonton, Canada. Foot Ankle Int. 2005; 26(11):932-936. doi: 10.1177/107110070502601106. PMID: 16309606 [DOI] [PubMed] [Google Scholar]
- 29. The National Electronic Injury Surveillance System: A Tool for Researchers Division of Hazard and Injury Data Systems U.S. Consumer Product Safety Commission. System. 2000. Accessed May 1, 2022. https://www.cpsc.gov/Research–Statistics/NEISS-Injury-Data [Google Scholar]
- 30. U.S. Census Bureau. Population and Housing Unit Estimates. Annu. Estim. Resid. Popul. United States, Reg. States, Puerto Rico. 2018. [cited 2021]. [Google Scholar]